Effect of Mammographic Screening Modality on Breast Density Assessment: Digital Mammography versus Digital Breast Tomosynthesis

Abstract

Background Breast Imaging Reporting and Data System (BI-RADS) breast density categories assigned by interpreting radiologists often influence decisions surrounding supplemental breast cancer screening and risk assessment. The landscape of mammographic screening continuously evolves, and different mammographic screening modalities may result in different perception of density, reflected in different assignment of BI-RADS density categories. Purpose To investigate the effect of screening mammography modality on BI-RADS breast density assessments. Materials and Methods Data were retrospectively analyzed from 24 736 individual women (42.3% [10 455 of 24 736] white women, 57.7% [14 281 of 24 736] black women; mean age, 56.3 years; age range, 40.0-74.9 years) who underwent from one to seven mammographic screening examinations from September 2010 through February 2017 (60 766 examinations). Three screening modalities were used: digital mammography alone (8935 examinations); digital mammography with digital breast tomosynthesis (DBT; 30 779 examinations); and synthetic mammography with DBT (21 052 examinations). Random-effects logistic regression analysis was performed to estimate the likelihood of assignment to high versus low BI-RADS density category according to each modality, adjusted for ethnicity, age, body mass index (BMI), and radiologist. The interactions of modality with ethnicity and BMI on density categorization were also tested with the model. Results Women screened with DBT versus digital mammography alone had lower likelihood regarding categorization of high density breasts (digital mammography and DBT vs digital mammography: odds ratio, 0.69 [95% confidence interval: 0.61, 0.80], P < .001; synthetic mammography and DBT vs digital mammography: odds ratio, 0.43 [95% confidence interval: 0.37, 0.50], P < .001). Lower likelihood of high density was also observed at synthetic mammography and DBT compared with digital mammography and DBT (odds ratio, 0.62; 95% confidence interval: 0.56, 0.69; P < .001). There were interactions of modality with ethnicity (P = .007) and BMI (P = .003) on breast density assessment, with greater differences in density categorization according to modality observed for black women than for white women and groups with higher BMI. Conclusion Breast density categorization may vary by screening mammographic modality, and this effect appears to vary by ethnicity and body mass index. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Philpotts in this issue.

Figure 1:

Flowchart shows inclusion and exclusion criteria for cross-sectional screening sample analyzed in our study. BI-RADS = Breast Imaging Reporting and Data System, BMI = body mass index.

Figure 2:

Histograms of Breast Imaging Reporting and Data System density categorization across different body mass index groups according to screening mammographic modality and ethnicity (black women and white women). BMI = body mass index, DBT = digital breast tomosynthesis, DM = digital mammography, SM = synthetic mammography.

Figure 3:

Craniocaudal (left) and mediolateral-oblique (right) consecutive digital mammography (DM) digital breast tomosynthesis (DBT) images (top) and, 1.1 years later, the synthetic mammography (SM) and DBT screening images (bottom) of the same postmenopausal white woman interpreted by the same radiologist. The DM and DBT screening examination was assigned Breast Imaging Reporting and Data System (BI-RADS) density category c (ie, dense), whereas the synthetic mammography and DBT screening examination was assigned BI-RADS density category b (ie, nondense). BMI = body mass index.

Figure 4:

Craniocaudal (left) and mediolateral-oblique (right) images from consecutive digital mammography (DM) and digital breast tomosynthesis (DBT) images (top) and 2.1 years later the synthetic mammography (SM) and DBT screening images (bottom) of the same postmenopausal black woman interpreted by the same radiologist. The digital mammography and DBT screening examination (top) was assigned Breast Imaging Reporting and Data System (BI-RADS) density category c (ie, dense), whereas the synthetic mammography and DBT screening examination was assigned BI-RADS density category b (ie, nondense). BMI = body mass index.